Damian Put has discovered a boundary error in the pefromupx() function
used by the UPX extraction module, which unpacks PE Windows executable
files. Both the "clamscan" command-line utility and the "clamd" daemon
are affected.

Impact

By sending a malicious attachment to a mail server running ClamAV, a
remote attacker can cause a Denial of Service and potentially the
execution of arbitrary code with the permissions of the user running
ClamAV.